Conventionally, in the manufacture of semiconductor devices, micro-processing by lithography using a photoresist has been carried out. The micro processing is a processing method comprising forming a photoresist coating on a semiconductor substrate such as a silicon wafer or the like, irradiating actinic rays such as ultraviolet rays through a mask pattern on which a pattern for a semiconductor device is depicted, developing it to obtain a photoresist pattern, and etching the substrate using the photoresist pattern as a protective film, thereby forming fine unevenness corresponding to the pattern on the surface of the substrate.
In the processing method, an organic underlayer coating being an underlayer coating comprising an organic material, such as an anti-reflective coating or a flattening costing is often formed. In this case, firstly the organic underlayer coating is removed by etching by using a photoresist pattern as a protective coating. The etching of the organic underlayer coating is generally carried out by dry etching. However, in this process not only the organic underlayer coating but also the photoresist are etched to cause a problem that the film thickness of the photoresist is reduced. Therefore, there is a tendency that organic underlayer coatings with a high removal rate by dry etching are used. However, as photoresists are composed of organic materials similarly to the organic underlayer coatings, it is difficult to suppress a decrease in film thickness of photoresists.
In recent years, the use of photoresists in a form of thin film has been considered with the progress of miniaturization in size to be processed. This is because it is supposed to occur fall of photoresist pattern or the like as aspect ratio (height/width) of photoresist pattern becomes large in case where the size of photoresist pattern is reduced without change of film thickness. In addition, photoresists are improved in resolution as the film thickness thereof becomes smaller. Consequently, it is required to use photoresists in a form of thin film. However, in case where a photoresist and an organic underlayer coating are used, there is problem that the film thickness of photoresist is reduced on removal of the organic underlayer coating as mentioned above. Thus, when photoresists in a form of thin film are used, there occurs a problem that it is not able to secure a film thickness sufficient as a protective coating (composed of a photoresist and an organic underlayer coating) for the processing of semiconductor substrate.
On the other hand, a coating composed of inorganic materials that is known as a hard mask has been used as an underlayer coating between a semiconductor substrate and a photoresist in this case, as the photoresist (organic material) is greatly different from the hard mask (inorganic material) in their constitutional components, the removal rate thereof drastically depends on the kind of gas used for dry etching. The suitable selection of the kind of the gas makes possible to remove the hard mask (underlayer coating) by dry etching without a large decrease of film thickness of the photoresist Therefore, in case where a photoresist and a hard mask are used, it is expected that it is able to secure a film thickness sufficient as a protective coating (composed of a photoresist and a hard mask) for the processing of semiconductor substrate even the photoresist is in a form of thin film.
Conventionally, hard masks are formed by a vapor deposition method by use of a CVD apparatus, a vacuum vapor deposition apparatus, and a sputtering apparatus, etc. On the contrary, photoresists and organic underlayer coatings are formed by application with a spin-coating apparatus or the like on a semiconductor substrate and then baking (hereinafter, referred to as “spin-coating method”). The spin-coating method is simple from viewpoint of apparatus used or the like compared with the vapor deposition method. Therefore, there are demands for hard masks that can be formed by a spin-coating method not a vapor deposition method. In the meantime, some underlayer coatings containing Inorganic materials are known (see, for example Patent Documents 1, 2 and 3).    Patent Document 1: JP-A-2001-3068 (2001)    Patent Document 2: JP-A-2001-242630 (2001)    Patent Document 3: JP-A-2003-177206 (2003)